1. Field of the Invention
The present invention relates to an agent for preventing, improving or treating hypertension, which permits inhibiting the rise of blood pressure and moreover improving hypertension and is useful as food and drink, and food such as food for specific health in addition to a drug for preventing, improving or treating hypertension.
2. Description of the Background Art
Cardiac diseases such as angina pectoris, myocardial infarction and heart failure, and cerebrovascular diseases such as cerebral infarction, cerebral hemorrhage and subarachnoid hemorrhage very closely relate to hypertension and stand second and third, respectively, in the Japanese causes of death. According to the basis research (the 1998 year) of the national life by the Ministry of Health and Welfare, the number of patients going to hospital regularly with hypertension is sixty-four per thousand in Japan and stands first in the cause of decease. As a countermeasure against the hypertension, may be mentioned the use of antihypertensive drugs such as diuretics, sympatholytic depressants, vasodilators and angiotensin converting enzyme inhibitors. These drugs are mainly applied to serious patients of hypertension. On the other hand, general treatments aiming at improving life custom, such as dietetic therapy, therapeutic exercise and restriction of smoking and drinking, are widely applied to slight and serious patients of hypertension. Therefore, the importance of general treatments is recognized. Among others, improvement in the custom of eating is said to be important, and there are many foods traditionally said to have a hypotensive effect. Antihypertensive materials derived from food have heretofore been extensively searched, and isolation and identification of active ingredients having a hypotensive effect have been made in large numbers. Juices of immature fruits of apple, sand pear, peach and the like, which belong to Rosaceae, contain fruit polyphenol having an inhibitory effect on an angiotensin I converting enzyme (ACE), and caffeic acid and chlorogenic acid have an ACE-inhibiting effect. It has been proposed to use such a fruit juice as an antihypertensive agent (Japanese Patent Application Laid-Open No. 259453/1996).
However, under the circumstances, many of drugs used for the purpose of treating hypertension are satisfactory in effectiveness, whereas patients are heavily burdened with their side effects, such as tachycardia and bradycardia, existing in no small numbers. With respect to foods said to have a hypotensive effect, or active ingredients thereof, the effectiveness is not always satisfactory. Further, many of them require a long time to develop a hypotensive effect.